This invention generally relates to interconnected systems of wireless local area networks (WLANs) and cellular networks. In particular, the invention relates to routing packets within such systems.
FIG. 1 is a simplified illustration of a cellular network 30 and a wireless local area network (WLAN) 22. A subscriber 20 has a subscription to both a WLAN 22 and a cellular network 30. WLANs, such as WLAN 22, are typically used to provide high speed data services to hot spot areas.
The WLAN 22 has a WLAN access point (WLAN-AP) 24 so that the subscriber 20 can access the WLAN 22 and a WLAN access router (WLAN-AR) 26 for routing packets coming into and leaving the WLAN 22, via the Internet 28.
The cellular network 30 has a radio access network 32 so that the subscriber 20 can access the network 30 and a cellular core network 34. The cellular core network 34 has a cellular gateway router 30 for routing packets coming into and leaving the cellular system 30. The cellular core network 34 is also connected to the Internet 28.
For the subscriber 20 to utilize a wireless service, the subscriber 20 either utilizes the cellular system 30 or the WLAN 22. If the subscriber 20 is in the cellular system 30 and not within the WLAN 22, the subscriber 20 makes a wireless connection to the cellular access network 32. Packets are transferred between the cellular access network 32 and the cellular core network 34. The cellular gateway router 36 transfers packets between the cellular core network 34 and the Internet 28. The packets are routed through the Internet 28 to a desired node, such as a destination server.
If the subscriber 20 is within the WLAN 22, the subscriber 20 is considered to be roaming with respect to the cellular network 30. The subscriber 20 makes a wireless connection to the WLAN-AP 24. Packets are transferred between the WLAN-AP 24 and the WLAN-AR 26. The WLAN-AR 26 transfers packets between the WLAN 22 and the Internet 28. The packets are routed through the Internet 28 to/from a desired node.
When a subscriber 20 moves from the cellular network 30 into the WLAN 22, sending packets from the subscriber 20 to the desired node 38 via the WLAN 22 can be performed using standard IP-packet routing tools. The desired node 38 has not moved. However, sending IP-packets from the desired node 38 to the subscriber 20 via the WLAN 22 is more problematic. If the subscriber 20 has a static IP address, the network ID of the subscriber's IP address is still the same as the network ID of the IP address of the router 36 of the cellular network 30.
Mobile IP versions 4 (MobileIPv4) and 6 (MobileIPv6) provide solutions to this problem. In MobileIPv4,the subscriber informs the cellular gateway router of its new location. These additional functions of the cellular gateway router and the WLAN-AR are referred to as Home Agent and Foreign Agent functions. When the cellular gateway router 36 receives the subscriber's packets from the desired node 38, the router 36 forwards them to the WLAN-AR 26. The WLAN-AR 26 sends the packets to the IP address of the subscriber 20 using layer 2 address mapping procedures, such as ARP.
A drawback with this approach is that packets originating from the subscriber 20 going through the WLAN 22 are not visible to the cellular network 30 or router 36. Another drawback with this approach is the increased loading on the cellular gateway router 36, due to the routing of all the subscriber's incoming packets.
In MobileIPv6,the subscriber 20 sends a binding update to the cellular gateway router 36 and the desired node 38. The binding update has information about the new network (WLAN 22) that the subscriber 20 is attached to. The IP packets from the destination node 38 are now routed directly to the subscriber 20 bypassing the cellular gateway router 36 and using standard IP routing protocols. A drawback with this approach is that packets originating from and going to the subscriber are not visible to the cellular network.
In some cases, it is undesirable that the IP packets are not visible to the cellular network 30. One reason is the security protocols of the cellular system 30 are circumvented. Additionally, certain services of the cellular system 30 can not be utilized, such as access to the cellular network's packet services.
To allow all of the subscriber packets to be visible to the cellular network 30, reverse and/or forward tunneling can be used. As shown in FIG. 2, in reverse tunneling, the packets from the subscriber 20 in the WLAN 22 are routed through both the WLAN 22 and the cellular network 30. Packets are transferred between the routers (cellular gateway router 36 and WLAN-AR 26) via an IP network 29. Reverse tunneling is supported by Mobile IPv4 and it allows all of the packets to be visible to the cellular network 30.
For MobileIPv6,both forward and reverse tunneling are needed to make the packets visible to the cellular network 30. In forward tunneling, the packets are also routed through both the cellular network 30 and the WLAN 22.
By routing all the packets through the cellular gateway router 36, the cellular system 30 can maintain security and provide cellular network based packet services to the subscriber 20, even when located in WLAN 22. To illustrate, the cellular gateway router 36 may send packets to a screening/monitoring agent for security purposes. One drawback to both these approaches is that the loading on the cellular gateway router is increased.
To reduce the routing on the cellular gateway router 36, selective reverse tunneling may be used. In selective reverse tunneling, packets are either selectively routed through both the cellular network 30 and the WLAN 22 or only through the WLAN 22, on a packet by packet basis. Such packet by packet routing is undesirable, since it increases the processing load. Furthermore, such packet level granularity may not be needed for most applications.
Accordingly, it is desirable to have alternate approaches to cellular network and WLAN routing.